The present invention relates to vehicle suspensions, and more particularly to biasing elements for, and aftermarket conversions of, such suspensions.
Many types of vehicle suspension arrangements are well known. In recent years, it has become common to provide coil springs as biasing elements, with damping elements, commonly known as shock absorbers, connected between frame or unibody portions of the vehicle and suspension elements such as axle housings and pivotable arm members. In many cases, telescopic shock absorbers are mounted generally concentrically with coil springs. An examplary configuration has a spindle mount pivotally connected between upper and lower A-arms, a coil spring and coaxial shock absorber being interposed between the lower A-arm and a fixed point on the chassis. Another such configuration, known as the McPherson system, having a short axle housing or spindle rigidly connected at a bottom extremity of a shock absorber, a top extremity of the shock absorber being pivotally mounted to the vehicle chassis. A pivoting linkage locates the shock absorber bottom extremity and (for front suspensions, a suitable steering linkage) rotationaly orients the bottom extremity relative to a longitudinal axis of the shock absorber, a camber alignment of the suspension being maintained by the rigid connection of the axle housing or mount to the shock absorber. In this configuration, the unitary combination of the shock absorber, spring, and spindle or axle housing is known as a "McPherson strut".
In a significant number of cases, it is desired to change the ride height of the vehicle or other characteristics of the suspension. Accordingly, it has been common to substitute different springs and/or suspension components having different geometry. Also, increased ride height is sometimes achieved by inserting spacers between springs and connected suspension components.
A recent development is air suspension, wherein pressurized bellows are substituted for coil springs. However, the pressurized bellows of the prior art are incompatible with concentric mounting of shock absorbers. Another recent development is shock absorbers that are configured for receiving pressure air for selectively increased ride height, the pressure air augmenting conventional springs. A further development is hydraulic actuators that are substituted for conventional shock absorbers, the actuators being operable for changing the ride height. In typical "low-rider" applications, a downwardly extending piston rod of a hydraulic actuator connects to a lower suspension A-arm in place of a conventional shock absorber, an oppositely extending cylinder body being connected through a cut-down portion of the original coil spring to the vehicle chassis. An electrically driven pump feeds the single-acting actuator to change the ride height in response to operator input. A principal disadvantage of the low-rider actuators of the prior art is that they produce a particularly harsh ride with substantially no spring action because only about half of the original spring is utilized.
Thus there is a need for an adjustable vehicle suspension biasing element that is compatible with concentric shock absorber mounting and otherwise overcomes disadvantages of the prior art.